A post shared by Khloé (@khloekardashian) on Oct 12, 2018 at 8:14pm PDT

Kim's eldest daughter, five-year-old North, and all of Kourtney Kardashian's children – Mason, eight, Penelope, six, and three-year-old Reign - were missing from the celebrations.

Kim later shared her own tribute to her niece True, and posted a photo of North playing with her baby cousin.

"Cousin Love," the 37-year-old wrote alongside the photo, which shows her daughter wearing a pink dress and matching tie-dye socks while True is in a cute white dress paired with a silver bow.

And while she was absent from the celebrations, Kourtney also celebrated her niece's half-birthday with a never-before-seen shot of her in the hospital moments after True was born.

"The middle of the night when my niece true was born," the 39-year-old wrote. "Today she is 6 months old."

While Khloe marked her daughter's milestone, it was bittersweet as it also marked six-months since boyfriend Tristan Thompson's cheating scandal.

In two cryptic posts on her Instagram Story, Khloe seemingly reflected on her life since the basketball star's alleged infidelity, and kept her fans guessing about what the future holds for her and Tristan.

"In 6 months time you can either be in the same place or a better place," the first post read. "Focus everyday on improving your Health, Wealth, and Happiness. It will take time but you can make it happen."

In the second post, the quote read: "You become a master of your life when you learn how to control where your attention goes. Value what you give your energy and time to."